DMNB is an important organic intermediate and has special function and use such as using as a tracer of explosives and the like. The International Civil Aviation Organization (ICAO) issued a document in 1991 to require compulsorily that tracers shall be added in plastic explosives to facilitate the detection of explosives in airports, while DMNB may be used as a tracer in replacement of nitrotoluene. Besides, DMNB is one of the key raw materials for the synthesis of the substances in the category of 2-substitute-1,3-dioxo-4,4,5,5-tetramethylimidazoline. The substances in this category can exclusively capture NO and has important application in medical sector. DMNB is also one of the important raw materials for the synthesis of nitroxide radicals as a main component of molecular magnets. Therefore, it is a matter of significance to researching and developing an efficient, low-consumption, safe and green DMNB synthesis process.
Currently, the methods for synthesis of DMNB mainly include:
Seigle L. W. and Hass H. B. (J. Org. Chem. 1940, 5: 100) reported a method for preparing DMNB through reaction between sodium salt of 2-nitropropane and 2-halogen-2-nitropropane in ethanol solvent. The reaction formula is shown below:

Wherein: X is Cl, Br or I.
The reactant “sodium salt of 2-nitropapane” is prepared through the reaction between metal sodium and anhydrous ethanol at first and then reaction with 2-nitropropane. 2-halogen-2-nitropropane may be obtained through adding halogen into a NaOH solution of 2-nitropropane. When the halogen is Cl, Br and I respectively, the conversion rate of this synthesis reaction is only 9%, 37% and 43%. In this method, highly toxic 2-nitropropane needs to be used.
Tsunoda R. et al (Eur. J. Pharm. 1994, 262: 55) adopted a modified solution: nitropropane is mixed with a NaOH solution at first, then liquid bromine is dropwise added slowly while cooled with ice water, and then ethanol is added to obtain the product through heating and reflux. This method is convenient and its yield is as high as 65˜92%, but the quality of the product is poor. As reported in literature, the melting point of the obtained product is 129˜130° C. only. Moreover, highly toxic substances such as 2-nitropropane, bromine and the like also need to be used.
Jesse B. M. et al (Org. Lett. 2010, 12: 3522) reported that 2-nitropropane and NaH take reaction at first to generate carbanions, and then CAN (ceric ammonium nitrate) is used to prepare DMNB through oxidation. The yield is 52%. However, this process also needs to use dangerous raw materials such as 2-nitropropane, NaH and the like as well as expensive CAN, so it is not an appropriate synthesis process, either.
To summarize, the currently known methods for synthesis of DMNB all need to use dangerous chemicals, such as: 2-nitropropane, making the production process unsafe, so none of them is suitable for industrial production.